Multilayer optical barrier

ABSTRACT

A liquid lens architecture includes a transparent substrate, a multilayer thermoplastic polyurethane (TPU)-based membrane overlying at least a portion of the transparent substrate, and a liquid layer disposed between and abutting the transparent substrate and the multilayer thermoplastic polyurethane-based membrane. The TPU-based membrane may exhibit a reversible elastic response to imposed strains of up to approximately 2% and is configured to limit the transpiration of fluid to less than approximately 10−2 g/m2/day.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.17/404,155 filed, on Aug. 18, 2021, which is a Continuation of U.S.application Ser. No. 16/730,658 filed on 30 Dec. 2019, which claims thebenefit of priority under 35 U.S.C. § 119(e) of U.S. ProvisionalApplication No. 62/898,010, filed Sep. 10, 2019, the contents of whichare incorporated herein by reference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate a number of exemplary embodimentsand are a part of the specification. Together with the followingdescription, these drawings demonstrate and explain various principlesof the present disclosure.

FIG. 1 is a cross-sectional illustration of an example bi-layer (AB)polymer composite membrane according to some embodiments.

FIG. 2 is a cross-sectional illustration of an example tri-layer (ABA)polymer composite membrane according to some embodiments.

FIG. 3 is a cross-sectional illustration of an example multilayerpolymer composite membrane according to some embodiments.

FIG. 4 is a cross-sectional illustration of an example multilayerpolymer composite membrane including an antireflective coating accordingto further embodiments.

FIG. 5 illustrates an example method for forming and integrating amultilayer composite membrane with a liquid lens according to certainembodiments.

FIG. 6 shows the elastic and plastic deformation response for aliphaticTPU layers and example barrier layers according to some embodiments.

FIG. 7 is an illustration of exemplary augmented-reality glasses thatmay be used in connection with embodiments of this disclosure.

FIG. 8 is an illustration of an exemplary virtual-reality headset thatmay be used in connection with embodiments of this disclosure.

Throughout the drawings, identical reference characters and descriptionsindicate similar, but not necessarily identical, elements. While theexemplary embodiments described herein are susceptible to variousmodifications and alternative forms, specific embodiments have beenshown by way of example in the drawings and will be described in detailherein. However, the exemplary embodiments described herein are notintended to be limited to the particular forms disclosed. Rather, thepresent disclosure covers all modifications, equivalents, andalternatives falling within the scope of the appended claims.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Variable focus liquid lenses have been proposed for a variety ofapplications, including eyeglasses, cameras, camcorders, telescopes,binoculars, projectors, as well as tunable optics for artificial realityand augmented reality systems. As will be appreciated, liquid lenses mayenable improved imaging system flexibility over a wide variety ofapplications requiring rapid focusing. By integrating a liquid lens, animaging system may quickly change the plane of focus thereby providingsharper images regardless of the distance to the object being viewed.

In some example liquid lens architectures, a fixed volume of liquid maybe disposed between a rigid lens or substrate and a thin, transparentelastic membrane. In further liquid lens architectures, the enclosedvolume of liquid may be increased or decreased during operation of thelens. In each of the foregoing approaches, by moving the elasticmembrane the liquid within the lens assembly may be redistributed suchthat the curvature of the elastic membrane is changed. The changedcurvature of the liquid lens surface can vary the optical power of thelens.

A variety of materials may be used to form the elastic membrane.Thermoplastic polyurethanes (TPUs), for example, may provide excellentelastic response after stretching and annealing processes. AliphaticTPUs, due to their small crystal size and low crystallization of hardsegments, may be characterized by high optical clarity but poor liquidbarrier performance. On the other hand, aromatic TPUs may provide decentbarrier performance but are typically characterized by low opticalclarity due to a relatively large crystal size. Further materials suchas PET, PEVOH, and PVDF are brittle and typically exhibit aninadequately small elastic deformation region and are thus inadequatefor liquid lens systems when implemented as stand-alone layers.

Notwithstanding recent developments, it would be advantageous to providea transparent elastic membrane exhibiting a reproducible elasticresponse under small strains over multiple actuation cycles while havingeffective barrier layer properties.

The present disclosure relates generally to multilayer membranes,including bilayer and tri-layer structures, and more specifically tocompositions, multilayer architectures, and methods of manufacturingmultilayer membranes that may be integrated into liquid lenses. Forinstance, multilayer structures may include 5, 10, 20, 50, or moreindividual layers. Example membranes include thermoplastic polyurethane(TPU)-based multilayer structures. The disclosed multilayer membranesinclude at least one thermoplastic polyurethane layer and may beoptically transparent, an effective barrier layer to liquid lens fluids,and exhibit an elastic response under small strains over repeatedcycles.

As used herein, a layer or multilayer that is “transparent” or“optically transparent” may, in some examples, be characterized by atransmissivity within the visible spectrum of at least approximately 90%(e.g., 90, 95, 96, 97, 98, 99, 99.5, or 99.9%, including ranges betweenany of the foregoing values) and less than approximately 10% bulk haze.Furthermore, the disclosed multilayer membranes may serve as barrierlayers that, for example, limit the transpiration (diffusion) of aliquid lens fluid to less than approximately 10⁻² g/m²/day (e.g. lessthan approximately 10⁻³, 10⁻⁴, 10⁻⁵ or 10⁻⁶ g/m²/day, including rangesbetween any of the foregoing values).

The disclosed multilayer membranes may include two or more individualpolymer layers arranged in a stacked configuration. For instance, abilayer polymer membrane may have an A-B structure and a tri-layerpolymer membrane may have an A-B-A structure or an A-B-C structure,where each layer A or layer C may include an optically transparentaliphatic TPU layer or an optically transparent aromatic TPU layer andeach layer B may include an optically transparent barrier layer, such asa layer including polyvinylidene fluoride (PVDF),chlorotrifluoroethylene (CTFE) polymer, polyvinylidene chloride (PVDC),ethylene vinyl alcohol (EVOH) copolymer, or other fluoropolymers, andthe like. In certain embodiments, layer B or layer C may be thinner thanlayer A. In certain embodiments, the difference in the solubilityparameters of polymer A and polymer B may be less than 10 MPa^(1/2) orless than 5 MPa^(1/2), and the difference in the solubility parametersof polymer B and polymer C may be less than 10 MPa^(1/2) or less than 5MPa^(1/2). A further example structure may include an aromatic/aliphaticmultilayer, such as an A-C-A-C multilayer, which may further include oneor more additional polymer layers, such as a transparent barrier layer,e.g., B-A-C-A-C or B-A-C-A-C-B or B-A-C-A-C-B-A-C, etc.

In various bi-layer and tri-layer architectures, the total thickness ofthe multilayer membrane may be less than approximately 1 mm, e.g.,approximately 100 micrometers, approximately 200 micrometers,approximately 300 micrometers, approximately 400 micrometers,approximately 500 micrometers, approximately 750 micrometers, orapproximately 1000 micrometers, including ranges between any of theforegoing values, whereas the thicknesses of the individual polymerlayers A, B, and C may independently range from approximately 1micrometer to approximately 250 micrometers, e.g., approximately 1micrometer, approximately 2 micrometers, approximately 5 micrometers,approximately 10 micrometers, approximately 20 micrometers,approximately 30 micrometers, approximately 40 micrometers,approximately 50 micrometers, approximately 100 micrometers,approximately 150 micrometers, approximately 200 micrometers, orapproximately 250 micrometers, including ranges between any of theforegoing values.

According to further embodiments, a multilayer TPU-based membrane mayhave an A-B-A-B- . . . A-B-A stacked architecture, where each layer Amay include an optically transparent aliphatic TPU layer and each layerB may include an optically transparent aromatic TPU layer. A totalthickness of such a stacked architecture may be less than approximately1 mm, e.g., approximately 100 micrometers, approximately 200micrometers, approximately 300 micrometers, approximately 400micrometers, approximately 500 micrometers, approximately 750micrometers, or approximately 1000 micrometers, including ranges betweenany of the foregoing values. The thickness of each individual layer Aand layer B may independently range from approximately 50 nm toapproximately 10 micrometers, e.g., approximately 50 nm, approximately100 nm, approximately 200 nm, approximately 300 nm, approximately 400nm, approximately 500 nm, approximately 1000 nm, approximately 2000 nm,approximately 5000 nm, or approximately 10000 nm, including rangesbetween any of the foregoing values.

Example TPU materials may include polyester TPUs, polyether TPUs, andpolycaprolactone TPUs. Moreover, suitable TPUs may include aromatic TPUsand aliphatic TPUs. Aromatic TPUs may be based on isocyanates such asmethylene diphenyl diisocyanate (MDI), including MDI isomers such as2,2′-MDI, 2,4′-MDI, and 4-4′-MDI. Example aliphatic TPUs may be based onisocyanates such as hydrogenated methylene diphenyl diisocyanate (H12MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate(IPDI).

According to still further embodiments, a multilayer TPU-based membranemay include an A-B, A-B-A, A-B-C, or A-B-A-B- . . . stacked architectureas in the previous embodiments and may additionally include asupplemental stacked architecture over either or both sides of the A-B,A-B-A, A-B-C, or A-B-A-B- . . . multilayer structure. That is, accordingto some embodiments, a multilayer TPU-based membrane may have anA-B-A-B- . . . C-D-C-D stacked architecture or a D-C-D-C- . . .-A-B-A-B- . . . -C-D-C-D stacked architecture. The supplemental -C-D-C-Darchitecture may include a multilayer antireflective (ARC) coating, forexample.

The -C-D-C-D architecture, if provided, may be optically transparent andaccordingly exhibit less than approximately 10% bulk haze and atransmissivity within the visible spectrum of at least approximately90%. For instance, a -C-D-C-D antireflective coating may be configuredto maintain at least approximately 90% transmissivity over approximately10⁶ actuation cycles and an induced engineering strain of up toapproximately 2%. In some embodiments, the antireflective coating mayexhibit a reflectivity within the visible spectrum of less thanapproximately 3%.

Layer C and layer D of a multilayer -C-D-C-D structure may include anysuitable dielectric materials, including silicon dioxide, zinc oxide,aluminum oxide, and magnesium fluoride, although additional dielectricmaterials are contemplated. For example, layer C and layer D of amultilayer -C-D-C-D structure may include polymer materials havingalternating high and low refractive indices.

Example high index polymers may include poly(pentabromophenylmethacrylate) (PPBPMA), poly(pentabromophenyl acrylate),poly(pentabromobenzyl methacrylate), poly(pentabromobenzyl acrylate),poly(2,4,6-tribromophenyl methacrylate), poly(vinylphenylsulfide),poly(1-napthyl methacrylate), poly(2, vinylthiophene),poly(2,6-dichlorostyrene), poly(N-vinylphthalimide),poly(2-chlorostyrene), and poly(pentachlorophenyl methacrylate).

Example low index polymers may includepoly(1,1,1,3,3,3-hexafluoroisopropyl acrylate) (PHFIA),poly(2,2,3,3,4,4,4-heptafluorobutyl acrylate),poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate),poly(2,2,3,3,3-pentafluoropropyl acrylate),poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate),poly(2,2,3,4,4,4-hexafluorobutyl acrylate),poly(2,2,3,4,4,4-hexafluorobutyl methacrylate),poly(2,2,3,3,3-pentafluoropropyl methacrylate),poly(2,2,2-trifluoroethyl acrylate), poly(2,2,3,3-tetrafluoropropylacrylate), poly(2,2,3,3-tetrafluoropropyl methacrylate), andpoly(2,2,2-trifluoroethyl methacrylate).

Layer C and layer D may each independently have a thickness ranging fromapproximately 1 nanometer to approximately 500 nanometers, e.g.,approximately 1, approximately 2, approximately 3, approximately 5,approximately 10, approximately 20, approximately 50, approximately 100,approximately 200, or approximately 500 nanometers, including rangesbetween any of the foregoing values.

In accordance with some embodiments, an antireflective coating (i.e., a-C-D-C-D structure) may operate to gradually decrease the refractiveindex between that of the multilayer TPU-based membrane and an adjacent,typically lower index material (e.g., air). In various embodiments, anantireflective coating may include multiple layers of varying refractiveindex and/or one or more layers having a refractive index gradient.

According to various embodiments, the multilayer TPU-based membranes maybe co-extruded or cast, stretched, and annealed to achieve an elasticresponse during actuation of a liquid lens.

Features from any of the embodiments described herein may be used incombination with one another in accordance with the general principlesdescribed herein. These and other embodiments, features, and advantageswill be more fully understood upon reading the following detaileddescription in conjunction with the accompanying drawings and claims.

The following will provide, with reference to FIGS. 1-8 , detaileddescriptions of multilayer TPU-based membranes and liquid lens designsincluding such membranes. The discussion associated with FIGS. 1-4includes a description of example multilayer (composite) TPU-basedmembrane architectures. As disclosed herein, multilayer (or composite)structures include two or more discrete polymer layers having differentpolymer compositions. The discussion associated with FIG. 5 includes adescription of a manufacturing method for forming a liquid lens having amultilayer TPU-based membrane. The discussion associated with FIG. 6includes a description of the mechanical behavior of example multilayermembranes. The discussion associated with FIGS. 7 and 8 relates toexemplary virtual reality and augmented reality devices that may includean optical element as disclosed herein.

Referring to FIG. 1 , illustrated is a cross-sectional view of aTPU-based bilayer membrane. Bilayer membrane 100 may include anoptically transparent aliphatic TPU layer or an optically transparentaromatic TPU layer 101 and a barrier layer 102 overlying the TPU layer101. In certain examples, barrier layer 102 may include one or more ofpolyvinylidene fluoride (PVDF), chlorotrifluoroethylene (CTFE) polymer,polyvinylidene chloride (PVDC), ethylene vinyl alcohol (EVOH) copolymer,or another fluoropolymer, etc.

According to some embodiments, FIG. 2 is an illustration of an exampletri-layer (ABA) TPU-based polymer membrane 200, where layers 201 mayeach include an optically transparent aliphatic TPU layer or anoptically transparent aromatic TPU layer, and intervening layer 202 mayinclude an optically transparent barrier layer, such as a polyvinylidenefluoride (PVDF) layer, a chlorotrifluoroethylene (CTFE) polymer layer, apolyvinylidene chloride (PVDC) polymer layer, an ethylene vinyl alcohol(EVOH) copolymer layer, a fluoropolymer layer, etc. The elastic modulusof the aliphatic or aromatic TPU layers 201 may be less than the elasticmodulus of the intervening barrier layer 202, which may inhibit thegeneration and/or propagation of cracks in any of the layers in responseto repeated actuation. As will be appreciated, although notunillustrated, a tri-layer TPU-based polymer membrane may have an ABCarchitecture, where the C layer may include a further opticallytransparent aliphatic or aromatic TPU layer or other opticallytransparent polymer layer.

In certain embodiments, the difference in the solubility parameters ofthe A and B layers in the embodiments of Examples 1 and 2 may be lessthan approximately 10 MPa^(1/2), e.g., less than approximately 5MPa^(1/2). In some embodiments, the thickness of each of the A layersmay be greater than the thickness of the B layer, and the total AB orABA structure thickness may be less than approximately 1 millimeter,e.g., less than approximately 500 micrometers or less than approximately300 micrometers.

According to further embodiments, FIG. 3 shows an example multilayerTPU-based membrane 300, where each layer 301 may include an opticallytransparent aliphatic TPU layer and each alternating layer 302 mayinclude an optically transparent aromatic TPU layer. The totalmultilayer extruded membrane thickness may be less than approximately 1millimeter, e.g., less than approximately 500 micrometers or less thanapproximately 300 micrometers. In certain embodiments, the thickness ofeach layer 302 may be less than approximately 10 micrometers, e.g., lessthan approximately 10 micrometers, less than approximately 1 micrometer,less than approximately 500 nm, or less than approximately 100 nm, whichmay inhibit the nucleation and growth of spherulite crystals duringannealing and the attendant degradation of optical properties, e.g., thegeneration of birefringence.

According to still further embodiments, FIG. 4 shows an exampleTPU-based membrane 400 having alternating polymer layers 401, 402 whereeach layer 401 may include an optically transparent aliphatic TPU layerand each layer 402 may include an optically transparent aromatic TPUlayer. A further alternating stack of layers 411, 412 may be formed overone or both surfaces of the multilayer 405. For instance, layers 411,412 may form an antireflective coating 415 where each layer 411 mayinclude a relatively low refractive index material and each layer 412may include a relatively high refractive index material, or vice versa.As used herein, a “low refractive index material” may, in some examples,be characterized by a refractive index of less than approximately 1.6,whereas a “high refractive index material” may, in some examples, becharacterized by a refractive index of approximately 1.6 or greater.

Referring to FIG. 5 , illustrated is an example method for forming andco-integrating a multilayer membrane having the requisite elasticresponse for actuation thereof. According to some embodiments, TPU-basedmultilayer membrane 500 (such as the multilayer membranes 100, 200, 300,or 400 described above with reference to any of FIGS. 1-4 ) may beformed in Step 1 using any suitable deposition process, such as castingor co-extrusion.

In Step 2, a stretching process may be used to form a strained membrane502. In some embodiments, the extent of induced strain may be up toapproximately 200%, e.g., less than approximately 200%, less thanapproximately 100%, less than approximately 50%, or less thanapproximately 10%, including ranges between any of the foregoing values.Referring to step 3, an optional annealing process may be used (e.g.,while maintaining the applied tension) to relax the polymer chainswithin strained membrane 502. By way of example, the annealingtemperature may be less than the melting temperature (T_(m)) and abovethe glass transition temperature (T_(g)) of the membrane, and theannealing time may vary from approximately 30 minutes to approximately24 hours, although lesser and greater annealing times may be used.

Following annealing, while maintaining the induced stress, the strainedmembrane 502 may be cooled (e.g., to approximately 23° C.) and, as shownschematically in Step 4, bonded to a transparent substrate 510. Theannealed membrane 502 may be affixed to one side of the substrate 510(Step 4 a) or to opposing sides of the substrate 510 (Step 4 b). A lensfluid 520 may be encapsulated between the strained membrane 502 and thesubstrate 510. Substrate 510 may include a lens or other opticallytransparent structure.

Substrate 510 may be a rigid, fluid impermeable structure and may, byway of example, include a material such as a polycarbonate, rubber,elastic polymer, or a glass plate. The lens fluid 520 encapsulated bythe substrate 510 and the membrane 502 may have an appropriate index ofrefraction and viscosity for use in a liquid lens and may includepolyphenyl ethers, polyphenyl thioethers, silicone oil, mineral oil,glycerin, or water, among others. Lens fluid 520 may be a clear ortinted fluid.

The deformation response of example membranes is shown in FIG. 6 , wheredashed lines 601, 602, 603, 604 represent aliphatic TPU layers (e.g.,layers 101, 201, 301, 401 in FIGS. 1-4 ) and dotted lines 605, 606, 607,608 represent barrier layers (e.g., layers 102, 202, 302, 402 in FIGS.1-4 ). According to various embodiments, FIGS. 6A, 6B, and 6C representdifferent cases of pre-stretch, annealing, and actuation. Segments 601and 605 represent elastic deformation regions, while segments 602 and606 represent plastic deformation regions. According to someembodiments, segments 603 and 607 represent the annealing relaxation ofthe respective layers, and segments 604 and 608 represent new elasticregions after annealing. The shaded zones 610 represent the strain areaunder actuation. In some embodiments, a TPU-based membrane may be placedin a state of uniaxial or biaxial tension, i.e., along one or moredirections parallel to a major surface of the membrane. In someembodiments, an in-plane line tension, which is the total force dividedby the total length of the perimeter of the film, of at leastapproximately 10 N/m (e.g., 10 N/m, 50 N/m, 100 N/m, 200 N/m, 300 N/m,400 N/m, 500 N/m, or more), including ranges between any of theforegoing values) may be applied to and maintained by a TPU-basedmembrane.

The stress-strain characteristics of aliphatic TPU layers and barrierlayers that are pre-stretched to plastic deformation regions 602, 606before annealing are shown in FIG. 6A. While maintaining tension, duringan annealing step, the respective layers may relax as illustrated bysegments 603, 607. After annealing, new elastic regions 604 and 608 aregenerated, where the deformation response during typical operation maycorrespond to the portions of segments 604, 608 within the shaded area610.

The stress-strain characteristics of aliphatic TPU layers and barrierlayers that are pre-stretched before annealing are shown in FIG. 6B. Inthe embodiment of FIG. 6B, the pre-stretched aliphatic TPU layers mayremain within an elastic region 601, whereas the barrier layers may bepre-stretched to a plastic deformation region 606. While maintainingtension during an annealing step, the respective layers may relax asillustrated by segments 603, 607. After annealing, new elastic regions604 and 608 are generated, where the deformation response during typicaloperation may correspond to the portions of segments 604, 608 within theshaded area 610. FIG. 6C describes both aliphatic TPU layers and barrierlayers that are pre-stretched and operated within membrane elasticregions without an annealing process.

Disclosed are thermoplastic polyurethane (TPU)-based multilayermembranes. Example multilayer polymer membranes may be opticallytransparent (>90%), provide an effective barrier layer, e.g., to liquidlens compositions, and exhibit a stable, reproducible elastic responseunder small strains over multiple cycles. According to certainembodiments, a bilayer TPU-based membrane may have an A-B stackstructure and a tri-layer TPU-based membrane may have an A-B-A or A-B-Cstacked structure, where each layer A or layer C may include anoptically transparent aliphatic or aromatic TPU layer and interveninglayer B may include an optically transparent barrier layer such as PVDF,ACLAR, or EVOH. In some embodiments, the barrier layer (layer B) may bethinner than the TPU layer (layer(s) A or C). In certain embodiments,the difference in the solubility parameters of polymer A and polymer Bmay be less than approximately 10 MPa^(1/2) or less than approximately 5MPa^(1/2). According to further embodiments, a multilayer membrane mayhave an A-B-A-B- . . . A-B-A stacked architecture, where each layer Amay include an optically transparent aliphatic TPU layer and each layerB may include an optically transparent aromatic TPU layer having athickness of less than approximately 10 micrometers, e.g., less than 500nm or less than 100 nm. According to still further embodiments, amultilayer membrane may further include a supplemental stackedarchitecture of alternating high- and low-refractive index layers thatform an antireflective coating. The multilayer TPU-based membranes maybe co-extruded, stretched, and annealed to achieve an elastic responseduring actuation of a liquid lens.

EXAMPLE EMBODIMENTS

Example 1: A liquid lens includes a transparent substrate, a multilayerthermoplastic polyurethane (TPU)-based membrane overlying at least aportion of the transparent substrate, and a liquid layer disposedbetween and abutting the transparent substrate and the multilayerthermoplastic polyurethane-based membrane.

Example 2: The liquid lens of Example 1, where the multilayerthermoplastic polyurethane-based membrane includes (a) a transparentthermoplastic polyurethane layer and (b) a transparent barrier layeroverlying the transparent thermoplastic polyurethane layer.

Example 3: The liquid lens of Example 2, where the transparentthermoplastic polyurethane layer includes an aliphatic thermoplasticpolyurethane layer or an aromatic thermoplastic polyurethane layer.

Example 4: The liquid lens of any of Examples 2 and 3, where thetransparent barrier layer includes a polymer selected frompolyvinylidene fluoride, chlorotrifluoroethylene, polyvinylidenechloride, and ethylene vinyl alcohol copolymer.

Example 5: The liquid lens of any of Examples 2-4, where the transparentbarrier layer is thinner than the transparent thermoplastic polyurethanelayer.

Example 6: The liquid lens of any of Examples 2-5, where a totalthickness of the multilayer thermoplastic polyurethane-based membrane isless than approximately 1 mm.

Example 7: The liquid lens of any of Examples 2-6, further including anantireflective coating directly overlying the transparent barrier layer.

Example 8: The liquid lens of any of Examples 2-7, including a furthertransparent thermoplastic polyurethane layer overlying the transparentbarrier layer.

Example 9: The liquid lens of Example 8, including an antireflectivecoating directly overlying the further transparent thermoplasticpolyurethane layer.

Example 10: The liquid lens of Example 1, where the multilayerthermoplastic polyurethane-based membrane includes a transparentaliphatic thermoplastic polyurethane layer and a transparent aromaticthermoplastic polyurethane layer overlying the transparent aliphaticthermoplastic polyurethane layer.

Example 11: The liquid lens of Example 10, where the multilayerthermoplastic polyurethane-based membrane includes alternating layers ofa transparent aliphatic thermoplastic polyurethane material and atransparent aromatic thermoplastic polyurethane material.

Example 12: The liquid lens of Example 11, where each of the alternatinglayers has a thickness of less than approximately 10 micrometers.

Example 13: The liquid lens of any of Examples 10-12, further includingan antireflective coating disposed directly over the multilayerthermoplastic polyurethane-based membrane.

Example 14: A liquid lens includes a transparent multilayerthermoplastic polyurethane-based membrane, the membrane having areversible elastic response to strains up to approximately 2% and beingconfigured to limit the transpiration of fluid therethrough to less thanapproximately 10⁻² g/m²/day.

Example 15: The liquid lens of Example 14, where the multilayerthermoplastic polyurethane-based membrane includes (a) a transparentthermoplastic polyurethane layer and (b) a transparent barrier layeroverlying the transparent thermoplastic polyurethane layer, where thetransparent barrier layer includes a polymer selected frompolyvinylidene fluoride, chlorotrifluoroethylene, polyvinylidenechloride, and ethylene vinyl alcohol copolymer.

Example 16: The liquid lens of Example 14, where the multilayerthermoplastic polyurethane-based membrane includes (a) a transparentaliphatic thermoplastic polyurethane layer and (b) a transparentaromatic thermoplastic polyurethane layer overlying the transparentaliphatic thermoplastic polyurethane layer.

Example 17: A method includes (a) forming a transparent thermoplasticpolyurethane layer over at least a portion of a transparent substrate,and (b) forming a transparent polymer layer directly over thetransparent thermoplastic polyurethane layer to form a multilayerthermoplastic polyurethane-based membrane.

Example 18: The method of Example 17, where the transparentthermoplastic polyurethane layer includes an aliphatic thermoplasticpolyurethane or an aromatic thermoplastic polyurethane.

Example 19: The method of any of Examples 17 and 18, where the polymerlayer includes a polymer selected from polyvinylidene fluoride,chlorotrifluoroethylene, polyvinylidene chloride, and ethylene vinylalcohol copolymer.

Example 20: The method of any of Examples 17-19, further includingapplying an in-plane tensile stress to the multilayer thermoplasticpolyurethane-based membrane.

Embodiments of the present disclosure may include or be implemented inconjunction with various types of artificial-reality systems. Artificialreality is a form of reality that has been adjusted in some mannerbefore presentation to a user, which may include, for example, a virtualreality, an augmented reality, a mixed reality, a hybrid reality, orsome combination and/or derivative thereof. Artificial-reality contentmay include completely computer-generated content or computer-generatedcontent combined with captured (e.g., real-world) content. Theartificial-reality content may include video, audio, haptic feedback, orsome combination thereof, any of which may be presented in a singlechannel or in multiple channels (such as stereo video that produces athree-dimensional (3D) effect to the viewer). Additionally, in someembodiments, artificial reality may also be associated withapplications, products, accessories, services, or some combinationthereof, that are used to, for example, create content in an artificialreality and/or are otherwise used in (e.g., to perform activities in) anartificial reality.

Artificial-reality systems may be implemented in a variety of differentform factors and configurations. Some artificial-reality systems may bedesigned to work without near-eye displays (NEDs). Otherartificial-reality systems may include an NED that also providesvisibility into the real world (e.g., augmented-reality system 700 inFIG. 7 ) or that visually immerses a user in an artificial reality(e.g., virtual-reality system 800 in FIG. 8 ). While someartificial-reality devices may be self-contained systems, otherartificial-reality devices may communicate and/or coordinate withexternal devices to provide an artificial-reality experience to a user.Examples of such external devices include handheld controllers, mobiledevices, desktop computers, devices worn by a user, devices worn by oneor more other users, and/or any other suitable external system.

Turning to FIG. 7 , augmented-reality system 700 may include an eyeweardevice 702 with a frame 710 configured to hold a left display device715(A) and a right display device 715(B) in front of a user's eyes.Display devices 715(A) and 715(B) may act together or independently topresent an image or series of images to a user. While augmented-realitysystem 700 includes two displays, embodiments of this disclosure may beimplemented in augmented-reality systems with a single NED or more thantwo NEDs.

In some embodiments, augmented-reality system 700 may include one ormore sensors, such as sensor 740. Sensor 740 may generate measurementsignals in response to motion of augmented-reality system 700 and may belocated on substantially any portion of frame 710. Sensor 740 mayrepresent a position sensor, an inertial measurement unit (IMU), a depthcamera assembly, a structured light emitter and/or detector, or anycombination thereof. In some embodiments, augmented-reality system 700may or may not include sensor 740 or may include more than one sensor.In embodiments in which sensor 740 includes an IMU, the IMU may generatecalibration data based on measurement signals from sensor 740. Examplesof sensor 740 may include, without limitation, accelerometers,gyroscopes, magnetometers, other suitable types of sensors that detectmotion, sensors used for error correction of the IMU, or somecombination thereof.

Augmented-reality system 700 may also include a microphone array with aplurality of acoustic transducers 720(A)-720(J), referred tocollectively as acoustic transducers 720. Acoustic transducers 720 maybe transducers that detect air pressure variations induced by soundwaves. Each acoustic transducer 720 may be configured to detect soundand convert the detected sound into an electronic format (e.g., ananalog or digital format). The microphone array in FIG. 7 may include,for example, ten acoustic transducers: 720(A) and 720(B), which may bedesigned to be placed inside a corresponding ear of the user, acoustictransducers 720(C), 720(D), 720(E), 720(F), 720(G), and 720(H), whichmay be positioned at various locations on frame 710, and/or acoustictransducers 720(I) and 720(J), which may be positioned on acorresponding neckband 705.

In some embodiments, one or more of acoustic transducers 720(A)-(F) maybe used as output transducers (e.g., speakers). For example, acoustictransducers 720(A) and/or 720(B) may be earbuds or any other suitabletype of headphone or speaker.

The configuration of acoustic transducers 720 of the microphone arraymay vary. While augmented-reality system 700 is shown in FIG. 7 ashaving ten acoustic transducers 720, the number of acoustic transducers720 may be greater or less than ten. In some embodiments, using highernumbers of acoustic transducers 720 may increase the amount of audioinformation collected and/or the sensitivity and accuracy of the audioinformation. In contrast, using a lower number of acoustic transducers720 may decrease the computing power required by an associatedcontroller 750 to process the collected audio information. In addition,the position of each acoustic transducer 720 of the microphone array mayvary. For example, the position of an acoustic transducer 720 mayinclude a defined position on the user, a defined coordinate on frame710, an orientation associated with each acoustic transducer 720, orsome combination thereof.

Acoustic transducers 720(A) and 720(B) may be positioned on differentparts of the user's ear, such as behind the pinna, behind the tragus,and/or within the auricle or fossa. Or, there may be additional acoustictransducers 720 on or surrounding the ear in addition to acoustictransducers 720 inside the ear canal. Having an acoustic transducer 720positioned next to an ear canal of a user may enable the microphonearray to collect information on how sounds arrive at the ear canal. Bypositioning at least two of acoustic transducers 720 on either side of auser's head (e.g., as binaural microphones), augmented-reality device700 may simulate binaural hearing and capture a 3D stereo sound fieldaround about a user's head. In some embodiments, acoustic transducers720(A) and 720(B) may be connected to augmented-reality system 700 via awired connection 730, and in other embodiments acoustic transducers720(A) and 720(B) may be connected to augmented-reality system 700 via awireless connection (e.g., a Bluetooth connection). In still otherembodiments, acoustic transducers 720(A) and 720(B) may not be used atall in conjunction with augmented-reality system 700.

Acoustic transducers 720 on frame 710 may be positioned along the lengthof the temples, across the bridge, above or below display devices 715(A)and 715(B), or some combination thereof. Acoustic transducers 720 may beoriented such that the microphone array is able to detect sounds in awide range of directions surrounding the user wearing theaugmented-reality system 700. In some embodiments, an optimizationprocess may be performed during manufacturing of augmented-realitysystem 700 to determine relative positioning of each acoustic transducer720 in the microphone array.

In some examples, augmented-reality system 700 may include or beconnected to an external device (e.g., a paired device), such asneckband 705. Neckband 705 generally represents any type or form ofpaired device. Thus, the following discussion of neckband 705 may alsoapply to various other paired devices, such as charging cases, smartwatches, smart phones, wrist bands, other wearable devices, hand-heldcontrollers, tablet computers, laptop computers, other external computedevices, etc.

As shown, neckband 705 may be coupled to eyewear device 702 via one ormore connectors. The connectors may be wired or wireless and may includeelectrical and/or non-electrical (e.g., structural) components. In somecases, eyewear device 702 and neckband 705 may operate independentlywithout any wired or wireless connection between them. While FIG. 7illustrates the components of eyewear device 702 and neckband 705 inexample locations on eyewear device 702 and neckband 705, the componentsmay be located elsewhere and/or distributed differently on eyeweardevice 702 and/or neckband 705. In some embodiments, the components ofeyewear device 702 and neckband 705 may be located on one or moreadditional peripheral devices paired with eyewear device 702, neckband705, or some combination thereof.

Pairing external devices, such as neckband 705, with augmented-realityeyewear devices may enable the eyewear devices to achieve the formfactor of a pair of glasses while still providing sufficient battery andcomputation power for expanded capabilities. Some or all of the batterypower, computational resources, and/or additional features ofaugmented-reality system 700 may be provided by a paired device orshared between a paired device and an eyewear device, thus reducing theweight, heat profile, and form factor of the eyewear device overallwhile still retaining desired functionality. For example, neckband 705may allow components that would otherwise be included on an eyeweardevice to be included in neckband 705 since users may tolerate a heavierweight load on their shoulders than they would tolerate on their heads.Neckband 705 may also have a larger surface area over which to diffuseand disperse heat to the ambient environment. Thus, neckband 705 mayallow for greater battery and computation capacity than might otherwisehave been possible on a stand-alone eyewear device. Since weight carriedin neckband 705 may be less invasive to a user than weight carried ineyewear device 702, a user may tolerate wearing a lighter eyewear deviceand carrying or wearing the paired device for greater lengths of timethan a user would tolerate wearing a heavy standalone eyewear device,thereby enabling users to more fully incorporate artificial-realityenvironments into their day-to-day activities.

Neckband 705 may be communicatively coupled with eyewear device 702and/or to other devices. These other devices may provide certainfunctions (e.g., tracking, localizing, depth mapping, processing,storage, etc.) to augmented-reality system 700. In the embodiment ofFIG. 7 , neckband 705 may include two acoustic transducers (e.g., 720(I)and 720(J)) that are part of the microphone array (or potentially formtheir own microphone subarray). Neckband 705 may also include acontroller 725 and a power source 735.

Acoustic transducers 720(I) and 720(J) of neckband 705 may be configuredto detect sound and convert the detected sound into an electronic format(analog or digital). In the embodiment of FIG. 7 , acoustic transducers720(I) and 720(J) may be positioned on neckband 705, thereby increasingthe distance between the neckband acoustic transducers 720(I) and 720(J)and other acoustic transducers 720 positioned on eyewear device 702. Insome cases, increasing the distance between acoustic transducers 720 ofthe microphone array may improve the accuracy of beamforming performedvia the microphone array. For example, if a sound is detected byacoustic transducers 720(C) and 720(D) and the distance between acoustictransducers 720(C) and 720(D) is greater than, e.g., the distancebetween acoustic transducers 720(D) and 720(E), the determined sourcelocation of the detected sound may be more accurate than if the soundhad been detected by acoustic transducers 720(D) and 720(E).

Controller 725 of neckband 705 may process information generated by thesensors on neckband 705 and/or augmented-reality system 700. Forexample, controller 725 may process information from the microphonearray that describes sounds detected by the microphone array. For eachdetected sound, controller 725 may perform a direction-of-arrival (DOA)estimation to estimate a direction from which the detected sound arrivedat the microphone array. As the microphone array detects sounds,controller 725 may populate an audio data set with the information. Inembodiments in which augmented-reality system 700 includes an inertialmeasurement unit, controller 725 may compute all inertial and spatialcalculations from the IMU located on eyewear device 702. A connector mayconvey information between augmented-reality system 700 and neckband 705and between augmented-reality system 700 and controller 725. Theinformation may be in the form of optical data, electrical data,wireless data, or any other transmittable data form. Moving theprocessing of information generated by augmented-reality system 700 toneckband 705 may reduce weight and heat in eyewear device 702, making itmore comfortable to the user.

Power source 735 in neckband 705 may provide power to eyewear device 702and/or to neckband 705. Power source 735 may include, withoutlimitation, lithium ion batteries, lithium-polymer batteries, primarylithium batteries, alkaline batteries, or any other form of powerstorage. In some cases, power source 735 may be a wired power source.Including power source 735 on neckband 705 instead of on eyewear device702 may help better distribute the weight and heat generated by powersource 735.

As noted, some artificial-reality systems may, instead of blending anartificial reality with actual reality, substantially replace one ormore of a user's sensory perceptions of the real world with a virtualexperience. One example of this type of system is a head-worn displaysystem, such as virtual-reality system 800 in FIG. 8 , that mostly orcompletely covers a user's field of view. Virtual-reality system 800 mayinclude a front rigid body 802 and a band 804 shaped to fit around auser's head. Virtual-reality system 800 may also include output audiotransducers 806(A) and 806(B). Furthermore, while not shown in FIG. 8 ,front rigid body 802 may include one or more electronic elements,including one or more electronic displays, one or more inertialmeasurement units (IMUs), one or more tracking emitters or detectors,and/or any other suitable device or system for creating an artificialreality experience.

Artificial-reality systems may include a variety of types of visualfeedback mechanisms. For example, display devices in augmented-realitysystem 700 and/or virtual-reality system 800 may include one or moreliquid crystal displays (LCDs), light emitting diode (LED) displays,organic LED (OLED) displays, digital light project (DLP) micro-displays,liquid crystal on silicon (LCoS) micro-displays, and/or any othersuitable type of display screen. Artificial-reality systems may includea single display screen for both eyes or may provide a display screenfor each eye, which may allow for additional flexibility for varifocaladjustments or for correcting a user's refractive error. Someartificial-reality systems may also include optical subsystems havingone or more lenses (e.g., conventional concave or convex lenses, Fresnellenses, adjustable liquid lenses, etc.) through which a user may view adisplay screen. These optical subsystems may serve a variety ofpurposes, including to collimate (e.g., make an object appear at agreater distance than its physical distance), to magnify (e.g., make anobject appear larger than its actual size), and/or to relay (to, e.g.,the viewer's eyes) light. These optical subsystems may be used in anon-pupil-forming architecture (such as a single lens configuration thatdirectly collimates light but results in so-called pincushiondistortion) and/or a pupil-forming architecture (such as a multi-lensconfiguration that produces so-called barrel distortion to nullifypincushion distortion).

In addition to or instead of using display screens, someartificial-reality systems may include one or more projection systems.For example, display devices in augmented-reality system 700 and/orvirtual-reality system 800 may include micro-LED projectors that projectlight (using, e.g., a waveguide) into display devices, such as clearcombiner lenses that allow ambient light to pass through. The displaydevices may refract the projected light toward a user's pupil and mayenable a user to simultaneously view both artificial-reality content andthe real world. The display devices may accomplish this using any of avariety of different optical components, including waveguide components(e.g., holographic, planar, diffractive, polarized, and/or reflectivewaveguide elements), light-manipulation surfaces and elements (such asdiffractive, reflective, and refractive elements and gratings), couplingelements, etc. Artificial-reality systems may also be configured withany other suitable type or form of image projection system, such asretinal projectors used in virtual retina displays.

Artificial-reality systems may also include various types of computervision components and subsystems. For example, augmented-reality system700 and/or virtual-reality system 800 may include one or more opticalsensors, such as two-dimensional (2D) or 3D cameras, structured lighttransmitters and detectors, time-of-flight depth sensors, single-beam orsweeping laser rangefinders, 3D LiDAR sensors, and/or any other suitabletype or form of optical sensor. An artificial-reality system may processdata from one or more of these sensors to identify a location of a user,to map the real world, to provide a user with context about real-worldsurroundings, and/or to perform a variety of other functions.

Artificial-reality systems may also include one or more input and/oroutput audio transducers. In the examples shown in FIG. 8 , output audiotransducers 806(A) and 806(B) may include voice coil speakers, ribbonspeakers, electrostatic speakers, piezoelectric speakers, boneconduction transducers, cartilage conduction transducers,tragus-vibration transducers, and/or any other suitable type or form ofaudio transducer. Similarly, input audio transducers may includecondenser microphones, dynamic microphones, ribbon microphones, and/orany other type or form of input transducer. In some embodiments, asingle transducer may be used for both audio input and audio output.

While not shown in FIG. 7 , artificial-reality systems may includetactile (i.e., haptic) feedback systems, which may be incorporated intoheadwear, gloves, body suits, handheld controllers, environmentaldevices (e.g., chairs, floormats, etc.), and/or any other type of deviceor system. Haptic feedback systems may provide various types ofcutaneous feedback, including vibration, force, traction, texture,and/or temperature. Haptic feedback systems may also provide varioustypes of kinesthetic feedback, such as motion and compliance. Hapticfeedback may be implemented using motors, piezoelectric actuators,fluidic systems, and/or a variety of other types of feedback mechanisms.Haptic feedback systems may be implemented independent of otherartificial-reality devices, within other artificial-reality devices,and/or in conjunction with other artificial-reality devices.

By providing haptic sensations, audible content, and/or visual content,artificial-reality systems may create an entire virtual experience orenhance a user's real-world experience in a variety of contexts andenvironments. For instance, artificial-reality systems may assist orextend a user's perception, memory, or cognition within a particularenvironment. Some systems may enhance a user's interactions with otherpeople in the real world or may enable more immersive interactions withother people in a virtual world. Artificial-reality systems may also beused for educational purposes (e.g., for teaching or training inschools, hospitals, government organizations, military organizations,business enterprises, etc.), entertainment purposes (e.g., for playingvideo games, listening to music, watching video content, etc.), and/orfor accessibility purposes (e.g., as hearing aids, visual aids, etc.).The embodiments disclosed herein may enable or enhance a user'sartificial-reality experience in one or more of these contexts andenvironments and/or in other contexts and environments.

The process parameters and sequence of the steps described and/orillustrated herein are given by way of example only and can be varied asdesired. For example, while the steps illustrated and/or describedherein may be shown or discussed in a particular order, these steps donot necessarily need to be performed in the order illustrated ordiscussed. The various exemplary methods described and/or illustratedherein may also omit one or more of the steps described or illustratedherein or include additional steps in addition to those disclosed.

The preceding description has been provided to enable others skilled inthe art to best utilize various aspects of the exemplary embodimentsdisclosed herein. This exemplary description is not intended to beexhaustive or to be limited to any precise form disclosed. Manymodifications and variations are possible without departing from thespirit and scope of the present disclosure. The embodiments disclosedherein should be considered in all respects illustrative and notrestrictive. Reference should be made to the appended claims and theirequivalents in determining the scope of the present disclosure.

Unless otherwise noted, the terms “connected to” and “coupled to” (andtheir derivatives), as used in the specification and claims, are to beconstrued as permitting both direct and indirect (i.e., via otherelements or components) connection. In addition, the terms “a” or “an,”as used in the specification and claims, are to be construed as meaning“at least one of.” Finally, for ease of use, the terms “including” and“having” (and their derivatives), as used in the specification andclaims, are interchangeable with and have the same meaning as the word“comprising.”

It will be understood that when an element such as a layer or a regionis referred to as being formed on, deposited on, or disposed “on” or“over” another element, it may be located directly on at least a portionof the other element, or one or more intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, it may be located on at least aportion of the other element, with no intervening elements present.

While various features, elements or steps of particular embodiments maybe disclosed using the transitional phrase “comprising,” it is to beunderstood that alternative embodiments, including those that may bedescribed using the transitional phrases “consisting of” or “consistingessentially of,” are implied. Thus, for example, implied alternativeembodiments to a TPU-based membrane that comprises or includes analiphatic compound include embodiments where a TPU-based membraneconsists essentially of an aliphatic compound and embodiments where aTPU-based membrane consists of an aliphatic compound.

What is claimed is:
 1. A liquid lens comprising: a transparentsubstrate; a multilayer membrane overlying the transparent substrate,the multilayer membrane comprising two or more thermoplasticpolyurethane layers; and a liquid layer disposed between the transparentsubstrate and the multilayer membrane.
 2. The liquid lens of claim 1,wherein the multilayer membrane comprises a transparent aliphaticthermoplastic polyurethane layer and a transparent aromaticthermoplastic polyurethane layer.
 3. The liquid lens of claim 1, whereina total thickness of the multilayer membrane is less than approximately1 mm.
 4. The liquid lens of claim 1, wherein the multilayer membranecomprises alternating layers of a transparent aliphatic thermoplasticpolyurethane material and a transparent aromatic thermoplasticpolyurethane material.
 5. The liquid lens of claim 4, wherein each ofthe alternating layers has a thickness of less than approximately 10micrometers.
 6. The liquid lens of claim 1, wherein the multilayermembrane comprises a transparent barrier layer.
 7. The liquid lens ofclaim 6, wherein the transparent barrier layer comprises a polymerselected from the group consisting of polyvinylidene fluoride,chlorotrifluoroethylene, polyvinylidene chloride, and ethylene vinylalcohol copolymer.
 8. The liquid lens of claim 1, further comprising anantireflective coating disposed directly over the multilayer membrane.9. The liquid lens of claim 1, wherein the multilayer membrane isconfigured to have a reversible elastic response to strains up toapproximately 2% and to limit transpiration of fluid therethrough toless than approximately 10⁻² g/m²/day.
 10. A liquid lens comprising: atransparent substrate; a multilayer membrane overlying the transparentsubstrate, the multilayer membrane comprising alternating layers of athermoplastic polyurethane and an optically transparent polymer; and aliquid layer disposed between the transparent substrate and themultilayer membrane.
 11. The liquid lens of claim 10, wherein thethermoplastic polyurethane layers comprise a transparent aliphaticthermoplastic polyurethane material or a transparent aromaticthermoplastic polyurethane material.
 12. The liquid lens of claim 10,wherein the optically transparent polymer layers comprise a polymerselected from the group consisting of polyvinylidene fluoride,chlorotrifluoroethylene, polyvinylidene chloride, and ethylene vinylalcohol copolymer.
 13. The liquid lens of claim 10, wherein a thicknessof each thermoplastic polyurethane layer is greater than a thickness ofeach optically transparent polymer layer.
 14. A method comprising:forming alternating layers of a transparent thermoplastic polyurethanelayer and a transparent polymer layer over a transparent substrate; toform a multilayer membrane; and forming a liquid layer between thetransparent substrate and the multilayer membrane to form a liquid lens.15. The method of claim 14, wherein the transparent thermoplasticpolyurethane layer comprises an aliphatic thermoplastic polyurethanematerial or an aromatic thermoplastic polyurethane material.
 16. Themethod of claim 14, wherein the transparent polymer layer comprises apolymer selected from the group consisting of polyvinylidene fluoride,chlorotrifluoroethylene, polyvinylidene chloride, and ethylene vinylalcohol copolymer.
 17. The method of claim 14, wherein a thickness ofthe transparent thermoplastic polyurethane layer is greater than athickness of the transparent polymer layer.
 18. The method of claim 14,further comprising forming an antireflective coating over the multilayermembrane.
 19. The method of claim 14, further comprising applying anin-plane tensile stress to the multilayer membrane.
 20. The method ofclaim 14, further comprising forming a liquid layer over the multilayermembrane.